/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2003 Robert Osfield 
 *
 * This library is open source and may be redistributed and/or modified under  
 * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or 
 * (at your option) any later version.  The full license is in LICENSE file
 * included with this distribution, and on the openscenegraph.org website.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
 * OpenSceneGraph Public License for more details.
*/
#ifndef OSGUTIL_HALFWAYMAPGENERATOR_
#define OSGUTIL_HALFWAYMAPGENERATOR_

#include <osgUtil/Export>

#include <osgUtil/CubeMapGenerator>

namespace osgUtil
{

	/** This cube map generator produces an Half-way vector map, useful for 
	    hardware-based specular lighting effects.
	    It computes: C = normalize(R - L), where C is the resulting color, 
	    R is the reflection vector and L is the light direction.
	*/
	class OSGUTIL_EXPORT HalfWayMapGenerator: public CubeMapGenerator {
	public:
		HalfWayMapGenerator(const osg::Vec3 &light_direction, int texture_size = 64);
		HalfWayMapGenerator(const HalfWayMapGenerator &copy, const osg::CopyOp &copyop);

	protected:
		virtual ~HalfWayMapGenerator() {}
		HalfWayMapGenerator &operator=(const HalfWayMapGenerator &) { return *this; }

		inline virtual osg::Vec4 compute_color(const osg::Vec3 &R) const;

	private:
		osg::Vec3 ldir_;
	};

	// INLINE METHODS

	inline osg::Vec4 HalfWayMapGenerator::compute_color(const osg::Vec3 &R) const
	{
		const osg::Vec3 V = (R / R.length()) - ldir_;
		return vector_to_color(V / V.length());
	}

}

#endif